科学新发现：夏天比冬天还让人觉得心情抑郁？

A new study looking at stress in medical students found that, counterintuitively, the “stress hormone” known as cortisol appears higher during the laid-back summer months.

一项针对医学院学生压力的新研究发现，与直觉恰恰相反，被称为皮质醇的“压力激素”在悠闲的夏季显得更高。

Researchers at Poznan University of Medical Sciences in Poland looked at levels of cortisol — a hormone that is released into the bloodstream in response to stress and helps regulate blood sugar and salt — at different times of the year.

波兰波兹南医科大学的研究人员在一年中的不同时间段研究了皮质醇水平，皮质醇是一种被释放到血液中以应对压力，帮助调节血糖和盐的激素。

They took saliva samples from medical students on two nonconsecutive days during the summer and did the same for two nonconsecutive winter days. Samples were collected for a full 24-hour period to analyze daily fluctuations in cortisol levels, which are typically higher in the morning. The study subjects tended to have higher cortisol levels in the summer.

他们在夏季每隔一天采集医学院学生的唾液样本，并在冬季每隔一天做同样的实验。样本要采集整整24个小时，以便分析皮质醇水平的每日波动情况，皮质醇水平通常在早上高点。研究对象的皮质醇水平在夏季往往更高。

Dominika Kanikowska, lead author of the study, says more research is needed, but the results are surprising.

该研究的第一作者多米尼克.卡尼科夫斯说，还要进行更多的研究，但目前的研究结果令人惊讶。

“We of course know seasonality in animals,” she says. “But more and more results show that seasonality is also connected with human beings.”

她说：“我们当然知道动物的季节性，但越来越多的研究结果表明，季节性也与人类有关。”